By the expression automatic transmission, used in the preamble, is to be understood both stepped and continuously variable automatic transmissions. Electrohydraulic automatic transmissions are composed of the following units: a starting unit such as a hydrodynamic converter, clutch/brakes, a hydraulic control device and an electronic transmission control device. The electronic transmission control device forms, from the input variables, the parameters required for control of the automatic transmission. Input variables are signals prepared by sensors and signals made available by other electronic control devices such as the engine control device. The electronic transmission control device controls, via output signals, the electromagnetic actuators which are in the hydraulic control device. Gearshifts are initiated, via the electromagnetic actuators, by selecting an adequate clutch/brake combination. The pressure distribution during the gearshift and the pressure level outside the gearshift are additionally controlled by the electromagnetic actuators.
From the prior art, for example DE-OS 40 41 253, automatic transmissions are known where the hydraulic control device is assembled on the underside. The hydraulic control device consists of one intake snorkel, one valve housing, one intermediate plate with a seal and one channel plate. Here the channel plate and the transmission housing come into contact by two surfaces. These two surfaces are designed as sealing surfaces. As a result of the setting properties, a change of the pre-load force of the clamping bolts and leakage can occur in this place. Since the hydraulic control device can only be partly wetted by the lubricant pan, leakage results in that the pump, via the intake channel, sucks air from the interior of the transmission instead of sucking hydraulic fluid from the lubricant pan.